We propose a comprehensive HER2 status assay for gene amplification detection with concomitant protein assessment and an internal control for chromosome 17 polysomy in a single brightfleld light microscope slide staining protocol. Gene copy, protein overexpression, and the internal control will be marked by different colored stains. This will also enable visualization and counterstalning of the underlying tissue morphology, and provide a permanent record with no signal loss over time. In sltu hybridization detection by enzyme metallography has been combined with Immunohistochemical protein staining using Fast red K to give high-resolution, deady distinguished concomitant gene and protein staining. A centromeric ohromosome 17 probe will be added as an internal control for chromosome 17 polysomy, detected using either a second metallographic signal converted to a colored product using photographic dye coupling chemistry, or enzymatic deposition of a different colored substrate. After optimization of the staining and metaliographic reagents and protocols, the new assay will be evaluated in a parallel controlled perspective study: a sedes of 104 tumors, previously evaluated by lmmunohistochemistry and in situ hybridization using FISH, GOLDFISH and enzyme metallography, will be evaluated using the new assay. HER2 will be a model for the development of a general method applicable to many cancers and to the future development of other multi-analyte assays and staining procedures.